World Class Water Chemistry By Accident? BRO Chemistry Session 8/5/2014
From Safe by Accident? by Judy Agnew & Aubrey Daniels Despite decades of reduction in safety related deaths and injuries on the job, catastrophic accidents appear to be on the rise. In the last ten years, there have been at least nine industrial accidents that resulted in more than 125 deaths.
From Safe by Accident? by Judy Agnew & Aubrey Daniels BP s Deepwater Horizon offshore oil rig operated for seven consecutive years without a single lost time incident or major environmental event. By these measures they were safe. Safe by Accident?
Supposedly World Class Stuff? We benchmark numbers going down each year No blade failures due to water chemistry No single phase FAC catastrophic failures Water Chemistry Related Boiler tube failures trending downward We have required cycle chemistry instrumentation We have training We have management support We measure carryover quarterly We conduct complete cation and anion analysis of cycle, stator systems, water plant quarterly We have boiler water chloride analyzers etc., etc., etc.
Last 36 months Operator not tripping unit when ph was below 7.0 Operator not tripping unit when boiler water chlorides were 30,000 ppb Open turbines and see deposition. Post chemical cleaning tube samples indicate unit not successfully chemical cleaned. Operator not tripping unit when boiler water chlorides were 15,000 ppb Tube deposit weight of over 70 g/ft2 Replacement of approximately 120 tubes due to severe pitting.
Assessment Is AEP s cycle water chemistry program world class by accident? We have everything we need to be successful so how does events like this occur at AEP? Should we accept these events as unavoidable events that just periodically happen?
A New Concept Repeat Situations Cycle Chemistry Influenced BTF and HTF Can Be Directly Related to Repeat Situations in Cycle Chemistry 2010 Paper Authored by Dr. Barry Dooley, Kevin Shields, Steve Shulder Structural Integrity Associates Inc.
Unintended Messages Is your cycle water instrumentation all in alarm on startup? Do you tell operators to ignore because it is due to CO2? What is the unintended message you send operators with this approach? Starting up unit more important than chemistry? Don t believe online instrumentation?
The Reality of Life One Ahh (bleep) wipes out all Atta boys This concept is AEP s attempt to eliminate the Ahh (bleep) that we have every 5 to 7 years. You will leave this years BRO Forum with the tools you need to use this concept.
Breakdown of Repeat Situations World Class Water Chemistry By Accident?
High Levels of Corrosion Product Corrosion product indicates a non optimized corrosion program. It can indicate flow accelerated corrosion is occurring. Very small increases in corrosion product transport can be significant Water chemistry influenced boiler tube failures start with tube deposition.
Where Do You Think All This Corrosion Product Went?
Severe FAC
High Levels of Corrosion Product (Subcritical/HRSG) Are you running Millipore's on your unit? Are your Millipore's snow white? Are you maintaining proper cycle ph per your unit specific chemical operating specification? Are your Dolan Lab feedwater total irons less than 5 ppb (dissolved iron <0.5 ppb) for subcritical/hrsg units? Are your Dolan Lab steam drum total iron less than 5 ppb (dissolved iron <0.5 ppb)? Are dissolved iron results samples at same conditions?
High Levels of Corrosion Product (Supercritical ) Are you running Millipore's on your deaerator inlet, deaerator outlet, economizer inlet, and hp heater drain? Are your Millipore's on your deaerator inlet, deaerator outlet, economizer inlet, and hp heater drain snow white? Are you maintaining proper cycle ph per your unit specific chemical operating specification? Are your Dolan Lab deaerator inlet, deaerator outlet, economizer inlet and hp heater drain sample total iron less then 3 ppb and/or dissolved iron less than 0.5 ppb? Are dissolved iron samples at same conditions?
High Boiler /HP Evaporator Deposition Is an indication of non optimized corrosion control of the condensate/feedwater cycle. For a subcritical unit is part of the mechanism for underdeposit corrosion tube failures (hydrogen damage, caustic gouging, acid phosphate attack)
>70 g/ft2 deposits
>100 g/ft2 deposits
High Boiler /HP Evaporator Deposition Are you experiencing phosphate hideout? Do you have piles of iron in your steam drum when you inspect steam drum? Are you experiencing any active underdeposit corrosion tube failures?
High Steam Generator Deposition Are chemical cleaning tube samples deposit thickness less then 40 micron (1.57 mils) Are prechemical cleaning samples taken from recommended locations per circular letter CH-O-Cl-010B Chemical Cleaning of Supercritical Units Is depoit thickness being used to determine need to chemical clean instead of deposit weight? Are you experiencing any supercritical waterwall cracking tube failures driven by ID deposits? Is dissolved oxygen detected at the hp heaters, economizer inlet cation conductivity below 0.15 mmhos, and the unit pressurized for a minimum of 2 hours before booster pump ph is allowed to be lowered during OT conversion during startup? Is booster pump specific conductivity increased and deaerator vents opened prior to removal of unit from service?
Non-Optimum Chemical Cleaning Chemical cleaning is the method used to remove deposition in our boilers and steam generators. This is a key tool in reducing the risk of underdeposit boiler tube failures on subcritical units AEP has recently had chemical cleans recently that have not removed all deposition.
Over 100 Waterwall Tube Leaks
Non-Optimum Chemical Cleaning Has it been more than 5 years for a subcritical or combined cycle unit since your last chemical cleaning? Are you using the proper chemical cleaning solvent for the deposits needing to be removed and the metallurgy of the unit? Are you maintaining proper temperatures during circulation? Are you ensuring proper circulation during chemical cleaning? Are you circulating chemicals for the required time?
Contaminant Ingress The introduction of sodium, chlorides and sulfates into the cycle from various sources, the most common being condenser leaks is also key in all water chemistry related boiler tube and turbine blade failures. These contaminants damage the protective passive layer and initiates damage mechanism.
SCC - Chlorides
Contaminant Ingress Subcritical/HRSG Are you experiencing hydrogen damage tube failures? Are you seeing turbine deposition due to chlorides, sodium, sulfate or silica during turbine outages? Are you exceeding action levels during contaminant ingress events? Are you operating with a condenser leak? Are you operating with attemperation sprays during condenser leaks? Do you track the amount of time core cycle chemistry parameters are within or outside of limits?
Contaminant Ingress - Supercritical Are you seeing turbine deposition due to chlorides, sodium, sulfate or silica during turbine outages? Are you exceeding action levels during contaminant ingress events? Are you operating with a condenser leak? At anytime including during resin transfer during regeneration, are you unable to maintain 100 % cleanup when operating with a condenser leak? Do you track the amount of time core cycle chemistry parameters are within or outside of limits?
Drum Carryover For subcritical & combined cycle units, drum carryover due to mechanical issues inside the steam drum or drum level control problems allows for chlorides, sulfates, and sodium to enter the steam circuits. These contaminants can initiate pitting and stress corrosion cracking (stainless material) in reheaters and superheaters. They can also initiate pitting of turbine blades that can lead to stress corrosion cracking and corrosion fatigue turbine blade failures
Drum Carryover Are you participating in the Dolan Lab Sampling Program? Do you know your % drum carryover? Do you have a sodium or cation conductivity spike on your saturated steam sample when you start your phosphate or caustic pump? Do you have phosphate or caustic on turbine when you perform inspection? Are you experiencing significant drum level swings during operation?
High Levels of Air in Leakage For subcritical units that have copper or copper alloy metallurgy in the condensate and feedwater cycle, the copper corrosion rate of this material is orders of magnitude higher when dissolved oxygen is present. Copper corrosion will redeposit in the boiler, superheat and more troubling on the HP turbine blades.
Copper Deposition on HP Turbine
High Levels of Air in Leakage Do you know what your air in leakage rate is? Are air in leakage tests performed? Does air in leakage change when equipment (FW heaters, condensate pumps, etc.) is placed into or removed from service?
Lack of Shutdown Protection All water chemistry related boiler tube and turbine blade failures start with the damaging of the protective passive layer. This layer needs to be protected 24/7 365 days/year when the unit is operating and also when the unit is out of service. If the protective layer is not damaged water chemistry related equipment failures will not occur. Failure mechanisms like pitting, stress corrosion cracking, and corrosion fatigue start with pits forming. These pits form when the unit is out of service. So if 99.99% of water chemistry related boiler tube and turbine blade issues are associate with condenser leaks, why do we not have a layup plan for the condenser?
Inadequate Shutdown Protection
Inadequate Shutdown Protection
Inadequate Shutdown Protection
Pitting and Stress Corrosion Cracking
Lack of Shutdown Protection Does a procedure exist that describes plant shutdown practices for layup protection of the unit? This includes condensate, feedwater, boiler, turbine, LP and HP drains. Is this procedure followed? Is dehumidification of the LP turbine being used on shutdown?
Inadequate On-Line and Alarmed Chemistry Instrumentation On-line instrumentation are our tools to inform operations that damaging conditions are present.
AEP Hydrogen Damage
Inadequate On-Line and Alarmed Chemistry Instrumentation Are required cycle chemistry instruments installed, trended and alarmed in control room? Do operators know how to respond to cycle chemistry alarms that initiate in control room? Are operators told to ignore certain alarms on startup? Is there a pm schedule to service and calibrate the instruments? Is the pm and calibration schedule being performed? Are operators decommissioning audible alarms because of unrealistic or unobtainable limits? Are cycle chemistry instruments removed from service because they are not working without another plan in place to monitor the parameter that is being compromised with the analyzer out of service?
Not Challenging the Status Quo One of the most damaging cultures to a water chemistry program is the that is the way we always have done it Or that plant is really screwed up that would never happen on my unit. Or repeat situations another Columbus boondoggle. They need to get a clue!!
If You Don t Look, This is What You Have
Not Challenging the Status Quo Subcritical/HRSG Will operators trip a unit on high steam sodium >24 ppb? Will operators trip unit on low boiler ph? Will operators remove subcritical from service when boiler water chlorides exceed 1000 ppb? Do we have a chemistry inspection plan during major outages to assess chemistry program success? Is the correct cycle chemistry being used? Do operators and/or chemists monitor unit chemistry and make changes prior to action levels Do chemist review and track Dolan Lab data? Are cycle samples taken and forwarded to Dolan Lab during upset conditions?
Not Challenging the Status Quo Supercritical Will operators trip a unit on high steam sodium >24 ppb? Will operators trip unit on low economizer inlet ph? Will operators remove unit from service when economizer inlet cation conductivity is 2 mmho for 5 minutes? Will operators remove unit from service when economizer inlet cation conductivity is 5 mmho for 2 minutes? Do we have a chemistry inspection plan during major outages to assess chemistry program success? Is the correct cycle chemistry being used? Do operators and/or chemists monitor unit chemistry and make changes prior to action levels Do chemist review and track Dolan Lab data? Are cycle samples taken and forwarded to Dolan Lab during upset conditions? Does the plant have a forum for communication with operators, maintenance, and performance on chemistry issues?
No Action Plan For the Above Repeat Situations Each repeat situation needs a tracking mechanism and action plan developed to remedy repeat situation. Are you operating with more than three repeat situations at the same time?
How Does Concept Work A 4 hour presentation is given to plant to introduce this concept. It is up to the plant to decide who attends this presentation, but it is recommended that it be a cross section of leadership, maintenance, operators and technicians (very similar to the BRO Team concept) After presentation, the lab team breaks away with the regional or central engineer and completes the repeat situation assessment.
How Does Concept Work There are two parts to the concept: Repeat Situation Assessment Daily Repeat Situation
Repeat Situation Assessment There are approximately 47 questions on the subcritical repeat situation checklist. There are approximately 43 questions on the supercritical repeat situation checklist. The assessment is completed by the lab (with help from central or regional engineering if required.)
Hoe Does Concept Work After assessment is complete and the ongoing repeat situations determined, the lab team presents the findings to the group that underwent the training. The group then votes on the on going repeat situations (similar to Lean) to determine which repeat situations will be addressed first. Team leads are assigned
How Does the Concept Work The daily repeat situations are the repeat situations that can change day to day. For instance you may not have a condenser leak today but you may have one tomorrow. When the leak occurs a repeat situation occurs Contaminant Ingress The lab team should be keeping track of the daily repeat situations. The goal is to keep from having three or more of the daily repeat situations occurring at the same time.
Daily Repeat Situations Are your Millipore's showing any color on your deaerator inlet, deaerator outlet, economizer inlet, or hp heater drain? Is cycle water ph operating outside required limits as defined in unit specific chemical operating specification? Are Dolan Lab deaerator inlet, deaerator outlet, economizer inlet and hp heater drains total iron (hot acid digestion) greater than 3 ppb and/or dissolved iron (acid soluble) greater than 0.5 ppb? Are chemical cleaning tube samples deposit thickness greater than 40 microns (1.57 mils)? Is conversion to OT on startup not following these minimum requirements: 1.) dissolved oxygen detected at the hp heaters prior to lowering cycle ph, 2.) economizer inlet cation conductivity below 0.15 mmho prior to closing deaerator vent. 3.) The unit pressurized for a minimum of 2 hours prior to closing deaerator vent?
Daily Repeat Situations Has it been more than 15 years since the unit has been chemical cleaned? Are you exceeding action levels during contaminate ingress events? Are you operating with a condenser tube leak? At any time including during resin transfer during regeneration, are you unable to maintain 100 % cleanup when operating with a condenser leak? Is layup shutdown procedure not being followed? Is dehumidification of the LP turbine not being used on shutdown? Is the pm and calibration schedule not being performed?
Daily Repeat Situations Are cycle chemistry instruments removed from service because they are not working without another plan in place to monitor the parameter that is being compromised with the analyzer out of service? Are there any standing cycle chemistry alarms in control room? Are you operating with more than three daily repeat situations at the same time?